Hi,
Centrino Duo isn't a processor per se, but rather a laptop platform (or marketing brand name) referring to the combination of a chipset, processor and wireless adapter.
As for multi-core processors, what your processor has is two cores operating at 1.66 GHz - this is how you should see it. Note however that a system with a dual core processor doesn't necessarily provide twice the performance of a system with a single core processor operating at the same clock speed.